This invention relates to a method and system for structured radiation production and, more specifically, a method and system of structuring radiation for surface measurement with a composite filter. The invention further relates to a method of making a composite filter.
As used herein, "light" means visible light, infrared light and ultraviolet light. An "interference material" or "interference filter" refers to materials or filters which use one or more material layers providing a bandpass function by interference of electromagnetic waves. An "interference reflectable electromagnetic radiation" is any electromagnetic radiation which is reflectable by an interference filter and includes at least radiation between long infrared and soft X-ray radiation. Reference to radiation or light at a particular wavelength shall include radiation or light in a pass band including the particular wavelength.
The production of a beam of radiation in which patterns of differing wavelength radiation are mingled in a controlled and stable manner have a number of uses. For example, the radiation may be a pattern of visible and infrared radiation used specifically for non-contact sensing of three-dimensional surfaces.
U.S. Pat. No. 4,349,277 entitled "Non-Contact Measurement of Surface Profile", issued Sept. 14, 1982 to Joseph L. Mundy, Gilbert B. Porter, and Thomas M. Cipolla, assigned to the assignee of the present invention, discloses a parallax method of surface measurement based upon optical triangulation. The Mundy el al, patent, the subject matter of which is hereby incorporated by reference, discloses the generation of a structured pattern of alternate wavelength light which is applied to the surface of an object. Separate detector arrays for the separate wavelengths of light are used to determine the profile of the object on which the structured light is applied.
The structured light in the Mundy et al patent is produced by use of a dichroic (interference) filter which separates light from a quartz-halogen tungsten lamp into separate visible and infrared beams. One beam is transmitted through the filter, whereas the other beam is reflected by the filter. The separate beams are reflected by a further pair of mirrors in order to intersect on different sides of an aluminum-on-glass mirror which has been selectively etched to remove aluminum and leave transparent stripes. As one beam passes through from one side of the aluminum-on-glass mirror and the other beam is reflected from the opposite side of the aluminum-on-glass mirror, the two beams recombine into a beam which regularly varies between infrared and visible light.
The Mundy et al. patent further discloses an alternate approach for producing the structured radiation or light by use of film spatial patterns, instead of the patterned aluminum-on-glass mirror. Two such patterns may be prepared and the transmissions of the film patterns would be complementary. An output beam splitter is used to combine the wavelength bands. This alternate approach is described in the subject Patent in Column 6, lines 44-56.